This invention relates generally to a tree harvesting machine and more particularly to the mounting of a felling or processing head on a free end of a boom in a manner permitting lateral swinging movement of the felling head.
Tree harvesting machines such as felling bunchers and felling processors typically have tree harvester heads pivotally mounted on the free end of the boom for enough lateral swinging movement to permit a cut tree to be bunched or laid upon the ground for processing. Various power operated mechanism have heretofore been used or suggested for pivoting the tree harvester heads, including ring gears driven by pinions rotated by hydraulic motors, a pinion driven by a chain, a pinion driven by a rack gear, a planetary gear drive and linear hydraulic actuators. For instance, U.S. Pat. No. 5,727,610 issued Mar. 17, 1998 to R. E. Isley for a Combined Tree Feller and Processor discloses a tree harvester head pivoted by operation of one or more hydraulically driven pinion gears meshing with a ring gear. The gearing of this and other tree harvester constructions is exposed to debris encountered in tree harvesting operations. Some tree harvesters have employed an exposed chain and sprocket arrangement which is subject to damage and excessive wear. Prior designs of rotating mechanisms for tree harvester heads have added an excessive amount of weight to the tree harvester. Excess weight results in additional cost of materials, reduction in payload capacity and increased power requirement for the prime mover.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a tree harvester head structure is pivotally supported on a mounting structure by a coupling which includes a rotary actuator and a bearing capable of carrying both axial and radial load. The rotary actuator is disposed at one of the radially inner and radially outer sides of the bearing and includes an annular housing component with an annular groove and an annular reaction component disposed within the groove. A vane is secured to the housing component in damming relation to the groove and a vane is secured to the reaction component in circumferentially spaced relation to the vane on the housing component. This positioning of the vanes divides the groove into two pressure chambers. The circumferential thickness of the vanes is sufficiently small to permit 300 degrees of relative rotation between the housing component and the reaction component; which translates to 300 degrees of lateral pivoting movement of the tree harvesting head. A spring applied and fluid pressure released brake between the mounting structure and the harvester head structure prevents lateral pivoting of the harvester head structure except when the rotary actuator is operated.